Magnetic mixers

ABSTRACT

The system and method of the invention pertains to an axial flux stator is implemented to replace the drive-end magnets and the drive motor. The axial flux stator comprises a control circuit to control the voltage and current provided to the stator, to measure the torque and speed of rotation, and to measure the magnetic flux and magnetic flux density produced by the axial flux stator and impeller magnets, individually or in combination. The axial flux stator comprises a plurality of current carrying elements to produce magnetic flux in an axial direction and drive the impeller.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of PCT International Application No.PCT/US2017/021412, having an International Filing Date of Mar. 8, 2017,which, in turn, claims priority to, and the benefit of, U.S. patentapplication Ser. No. 15/087,712, filed on Mar. 31, 2016, both of whichare herein incorporated by reference in their entirety.

FIELD

Embodiments relate generally to the field of bioreactors, and moreparticularly to a magnetic mixer drive for a bioreactor.

BACKGROUND

Mixers and pumps have a wide range of applications includingbioreactors. The main elements in a rotary mixer 100 (FIG. 1A) are thedrive 14 (which contains the driving mechanism) and the impeller 12(which contains the mixing blades), at the impeller end 11. The twoelements are aligned and coupled together by different topologies. Inone aspect, the magnetic coupling is where the impeller 12 holds a setof magnets 10 that are coupled to the drive end 13. This is establishedby a set of magnets in the drive end rotated by a separate motor. Theexisting technology contains a set of cylindrical magnets 14 (See FIG.1B) on each end separated by a certain “magnetic” gap 16 which isprimarily composed of air, fixing elements, and mixing bag wall whichare all non-magnetic elements. The existing technology suffers manyimpediments, including, but not limited to: (1) the weak couplingbetween the magnets which requires using more expensive and largermagnets (e.g., Neodymium magnets), (2) poor volume utilization, (3) theuse of rare-earth magnets in the impeller which is a single use elementthat increases the cost of the impeller and poses environmentalchallenges, and (4) large drive size, as it constructs of a set of largecoupling magnets driven by a separate electrical motor.

Mixing systems often include an agitator or impeller mechanicallyconnected to a drive shaft lowered into a fluid through an opening inthe top of a vessel. The drive shaft is connected to an electric motorarranged outside the vessel. In a closed vessel, a fluid seal isprovided between the drive shaft and the wall of the vessel to preventleakage of fluid from the vessel. Other mixing systems include arotating magnetic drive head outside of the vessel and a rotatingmagnetic impeller as an agitation element within the vessel. Themovement of the magnetic drive head enables torque transfer and thusrotation of the magnetic impeller allowing the impeller to mix andagitate the fluid within the vessel. Because there is no need in aclosed vessel to have a drive shaft penetrate the vessel wall tomechanically rotate the impeller, magnetically coupled systems caneliminate the need for having fluid seals between the drive shaft andthe vessel. Magnetic coupling of an impeller inside the vessel to adrive system or motor external to the vessel can eliminate contaminationissues, allow for a completely enclosed system, and prevent leakage.

Increasingly, in the biopharmaceutical industry, single use ordisposable containers or vessels are used as close type systems,typically in range of about 1-2000 liters. The vessel may be a tank-typesupport with for example substantially cylindrical shape and is made ofrigid material such as stainless steel to provide sufficient support forthe flexible bag or container, for example of a kind used in single-usebioreactors. Use of sterilized disposable bags eliminates time consumingsteps of cleaning of the vessel and reduces the chance of contamination.The flexible container or bag is placed inside the vessel in an accuratemanner so that for example different pipelines or tubes, mixers andsensors can be connected to the bag properly and accurately.

Combining the single use or disposable bags with a magnetic agitatorsystem establishes a sterile environment that is utilized inbiopharmaceutical manufacturing. A variety of vessels, devices,components and unit operations for mixing and manipulating liquidsand/or for carrying out biochemical and/or biological processes areavailable. For example, biological materials including mammalian, plantor insect cells and microbial cultures can be processed usingbioreactors that include single-use processing bags. Manufacturing ofcomplex biological products such as proteins, monoclonal antibodies,etc. requires, in many instances, multiple processing steps ranging fromfermentation or cell culture (bacteria, yeast, insect, fungi, etc.), toprimary recovery and purification.

It is desirable to address the needs as stated above by utilizing lessexpensive elements that are more environmentally friendly. Aspects ofthe invention will run a much smaller impeller, and have a reducedmagnetic force that will allow the bag to be separated from the drivemore easily. Further, moving parts on the drive (user) end will beaddressed to provide safer mechanisms.

The movement of the magnetic drive head enables torque transfer and thusrotation of the magnetic impeller allowing the impeller inside thevessel to mix and agitate the fluid within the vessel without providinga sealed shaft. The magnetic mixing principle is especially advantageouswhen using completely closed vessels, or when utilizing containers asrequired to maintain sterility of the internal volume and the fluid tobe mixed.

In single-use processing technology, as employed in the production ofbiopharmaceuticals, plastic containers and bags are used which aretypically pre-sterilized (e.g., by gamma irradiation), and employed ascompletely closed systems connected to adjacent fluid processingequipment and lines using aseptic connections. In these applications ofsingle-use mixing vessels and bioreactors, the use of magnetic mixingtechnology is preferred for reasons of process safety, simplicity andthe lower cost that comes by omitting complex sealing arrangementsaround rotating shafts.

Today, certain challenges are imposed on processes employing magneticmixing technology where a direct and permanent mechanical connectionbetween impeller and external drive by a shaft is lacking. Thesedeficiencies include not knowing the actual speed of the impeller; andthe torque and power input are more difficult to assess compared with adirect mechanical coupling. Further, as the power transferred bymagnetic couplings is generally limited compared to mechanical shafts,magnetic mixers are typically operating at lower power input which makesit difficult to assess power input and torque on the background offrictional forces, disturbances and noise in such measurements.Therefore, there is a need to improve the assessment, measurement andcontrol of magnetic mixing and magnetic mixer couplings.

In more details, challenges with current magnetic mixers include: (1)indirect (not real-time) determination of power delivered to the fluid,as performed with user-interface manipulation of formulas or look-uptables; (2) fluid density and/or viscosity changes as the mixing processtakes place, without accurate control of the mixing process; and (3)inability to identify abnormalities in the mixing process. No feature ordirect process in bioreactors used to date can detect or flag suchissues.

Moreover, no existing solution provides for a direct measure of thepower delivered to the fluid while mixing. Prior methods have beendependent on look-up tables to calculate the power delivered to fluid.In addition, no device or method has been able to continuously monitorthe fluid viscosity and density or to detect abnormalities in mixingprocess without the look-up tables as suggested prior.

It is desirable to address the needs as stated above by providingadditional functionality to a bioreactor and/or mixer. It will allowaccurate monitoring of the power delivered to the fluid while mixing,and will provide more accurate control by a user. It will alsobeneficially permit continuous updates of the fluid properties, andpreferentially, alarms in cases of abnormalities in mixing, such as, forexample, in the circumstance of ‘flooding’ of impellers when the ratioof volumetric gas to liquid ratio exceeds a threshold.

SUMMARY

The system and method of the invention pertains to a magnetic drive fora bioreactor mixer or pump that strengthens the magnetic coupling toprovide higher torque and replace the drive-end magnets and drive motor.Embodiments disclosed herein use a back iron on both ends to strengthenthe magnetic coupling as well as pie-shaped magnets (“pie” shaped in thesense of a wedge shape and format (i.e., triangular/trapezoidal have awider outer edge and smaller inner dimension, or shaped as a circular orannular sector) to increase the volume utilization and hence providehigher torque and allow the use of less expensive material (e.g.ferrites). In another embodiment, the rotor side is constructed with aHalbach array which increases the torque without the need to add a backiron piece. Another embodiment implements an axial flux stator toreplace the drive-end magnets and the drive motor.

In one embodiment, a system is described to be utilized as bioreactormixer, the system comprising: a rotation drive, an impeller capable ofrotating around a central (rotational) axis, and a plurality of magnetspositioned in one or more array formats, a first set of magnets in afirst array format positioned at a drive end adjacent the rotation driveand a second set of magnets in a second array format positioned at theimpeller; wherein the rotation drive is a drive stator.

In one aspect, the system has a drive stator that is an axial fluxstator. In another aspect, the axial flux stator is positioned on anunderside of the plurality of magnets. The axial flux stator comprises acontrol circuit to control the voltage and current, individually or incombination, provided to the stator. The axial flux stator comprises acontrol circuit to measure the torque and speed of rotation. The axialflux stator comprises a control circuit to measure the magnetic flux andmagnetic flux density produced by the axial flux stator and impellermagnets. The axial flux stator comprises a plurality of current carryingelements to produce magnetic flux in an axial direction and drive theimpeller.

The axial flux stator in embodiments described herein comprises a coreto fix the current carrying elements upon, or affix the current carryingelements thereto. Aspects of the embodiments disclosed thus permit thecore to be magnetic or non-magnetic.

Another embodiment is a mixing system comprising: a stator comprising aplurality of current carrying elements to produce a magnetic flux in anaxial direction, an impeller capable of rotating around an axis of theaxial flux stator; wherein the magnetic flux drives the impeller. Thestator is an axial flux stator having a core to affix the currentcarrying elements, the core including stator teeth. The core is magneticin one aspect, and may also be non-magnetic.

Various embodiments include an impeller comprising a plurality ofmagnets, a back plate to enhance the magnetic coupling, a plurality ofcurrent carrying elements, one or more mixing blades, and/or a fixtureto support the impeller from misalignment, alone or in combination.

One embodiment of a system is utilized as bioreactor mixer, the systemcomprising: a rotation drive, an impeller capable of rotating around acentral (rotational) axis, a plurality of magnets positioned in one ormore array formats, a first set of magnets in a first array formatpositioned at a drive end adjacent the rotation drive and a second setof magnets in a second array format positioned at the impeller, and atleast one plate including the first set of magnets positioned thereonsuch that the first set of magnets are positioned in a concentricgeometric configuration and individually shaped with a wider outsidedimension that narrows toward a center of the concentric geometricconfiguration; wherein the second set of magnets are arranged adjacentone another to augment a magnetic field on one side of the second arraywhile cancelling the magnetic field to zero on an opposite side of thesecond array to achieve a spatially rotating pattern of magnetization.In one aspect, the system further comprises an external vessel intowhich at least a portion of the bioreactor mixer is placed.

In another embodiment, a system is utilized as bioreactor mixer, thesystem comprising: a rotation drive, an impeller capable of rotatingaround a central (rotational) axis, a plurality of magnets positioned inone or more array formats, a first set of magnets in a first arrayformat positioned at a drive end adjacent the rotation drive and asecond set of magnets in a second array format positioned at theimpeller, and at least a first plate including the first set of magnetspositioned thereon; wherein the second set of magnets are positionedwith a second plate comprising a material having magnetic permeabilitygreater than the magnetic permeability of air and sandwiched between thefirst set of magnets and the impeller, such that a magnetic fieldgradient is created between the first array format of the first set ofmagnets and the second array format of the second set of magnets.

In one aspect, the first plate comprises a material having magneticpermeability greater than the magnetic permeability of air. The firstset of magnets can be positioned in an array format geometrically shapedwith a wider outside dimension that narrows toward a concentric center.The second set of magnets can be positioned in an array formatgeometrically shaped with a wider outside dimension that narrows towarda concentric center.

Embodiments of the invention disclose a system and method that utilize atorque sensor, and the measured torque associated with the sensor, todetect the different fluid and mixing properties, conditions, andabnormalities in a mixing process. The torque produced in the mixingprocess relates to different fluid properties such as viscosity anddensity. It also relates to different mixing conditions such as presenceof obstacles and changes or issue with gas sparging. Moreover, torquemeasurements enable determination of power transmitted to a fluid byactual measurement, in contrast to using solely empirical impeller powernumber and speed, and allow actual mass transfer determination (i.e.,gas transfer calculations).

Embodiments disclosed regard a torque sensor (e.g., transducer) and amethod of using the measured torque to detect the different fluid andmixing properties, conditions, and abnormalities.

In one embodiment, a magnetic mixing system characterizes conditions ina fluid mixing device, the system comprising: a vessel comprising afluid; a drive that creates a magnetic field; a controller that operatesthe drive; one or more sensors positioned with the system to detect themagnetic field or a magnetic flux; and a processor receiving informationfrom the sensors to calculate one or more of power provided to thefluid, torque and speed of the impeller. The magnetic mixing systemfurther comprises an impeller inside the vessel, wherein the drivecreates the magnetic field to rotate the impeller and the sensorsmeasure the magnetic field or the magnetic flux provided to theimpeller. The one or more sensors are positioned with the drive, theimpeller, or between the impeller and the drive. The sensors can furtherdetect current and voltage provided to the drive.

In one aspect, the drive as a stator, or the drive can include a set ofpermanent magnets in combination with a motor. In another aspect, thedrive is a stator, motor, or magnetic coupling, and the sensors aretransducers positioned therewith, respectively, alone or in combination.

Embodiments of the application, utilize the torque and speed of theimpeller as it corresponds to torque and speed in mixing of the fluid.The processor uses the power, torque or speed, alone or in combination,with one or more fluidic properties to assess real-time mixingconditions and mixing properties. In addition, the processor detects achange in the fluidic properties, mixing conditions, or mixingproperties, individually or in combination. In another embodiment, theprocessor detects abnormalities in the fluidic properties, mixingconditions, or mixing properties as determined by learned patterns orpredetermined threshold values. The fluidic properties include anynumber of characteristic compositions, including density and viscosityof the fluid, among others. The processor detects abnormalities in thedensity or viscosity of the fluid, in the power, torque, or speed, aloneor in combination. Further, the processor can detect blockage, gasdispersion, or one or more contaminants in the fluid, alone or incombination.

Embodiments disclosed herein provide a processor that is an analyzer toprovide direction to the controller in a feedback loop. The analyzerdirects power to the drive to increase or decrease agitation, to adjustfluidic properties, and correct any deficiencies or abnormalities,individually or in combination.

Thus described, one embodiment discloses a method of controllingconditions in a fluid mixing device, the method comprising the steps of:providing the fluid mixing device having a vessel comprising a fluid, adrive that creates a magnetic field, a controller that operates thedrive, one or more sensors, and a processor; detecting, by way of theone or more sensors, at least one of a magnetic field, a magnetic flux,power provided to the fluid, torque, speed, current, or voltage;calculating power, torque and speed of the impeller, if not previouslydetected; and analyzing, by way of the processor, using the power,torque and speed to determine one or more fluidic properties of thefluid, real-time mixing conditions and mixing properties. In one aspect,the mixing system further comprises an impeller and the step ofdetecting includes detecting a position of the impeller. The step ofanalyzing includes detecting a change in the fluidic properties.

In addition, the power, torque, speed, current, voltage, fluidicproperties, mixing conditions, and mixing properties, alone or incombination, are displayed at a user-interface. The power, torque andspeed are determined directly, without user manipulation.

Aspects of the disclosed embodiments include fluidic propertiescomprising fluid composition, density, and viscosity, alone or incombination, provided to the processor by way of the sensors. The methodfurther comprises a step of identifying abnormalities in the fluidmixing device, the fluidic properties, the mixing conditions, and themixing properties. The processor can be an analyzer that providesfeedback to the controller to automatically control the power, torque,and speed delivered to the drive. In one aspect, the processor providesa pre-determined composition, viscosity and density of the fluid, aloneor in combination. In another aspect, the processor provides informationto the controller that determines an optimal composition, viscosity, anddensity as based on a change in the fluidic properties.

Further aspects allow the sensors to detect any number of attributes,characteristics, or otherwise, including, without limitation, detectingan angle between the drive and the impeller during operation of thefluid mixing device in order to determine the fluidic properties.

Embodiments thus provide additional functionality to a user of thebioreactor or mixer. Accurate monitoring of power delivered to the fluidwhile mixing is now possible, in real-time, allows continuous updatesand adjustments as to the fluid properties. In another aspect, alarmsare implemented, as desired, in cases of abnormalities in the mixingprocess.

Detailed descriptions of various embodiments are described as follows.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A (PRIOR ART) illustrates the magnetic drive for a bioreactormixer.

FIG. 1B (PRIOR ART) illustrates a magnetic coupling where the impellerholds a set of magnets that are coupled to the drive end, the set ofmagnets in the drive end rotated by a separate motor.

FIG. 2 (PRIOR ART) depicts a cross-sectional view of the magnetic fieldcoupling in a prior art system.

FIG. 3 depicts a cross-sectional view of the magnetic field couplingwhen using the individual magnet shapes and configuration as disclosedin embodiments herein.

FIG. 4A illustrates an embodiment of the invention including a back ironon both ends.

FIG. 4B illustrates an embodiment including pie-shaped magnets,individually positioned, angled, and spaced in a magnetic arrangementaround a central axis.

FIG. 4C illustrates the rotor side constructed with a Halbach array inanother embodiment, the individual magnets adjacent one another withoutspacing to form a concentric magnetic arrangement.

FIG. 5 depicts a cross-sectional view showing the magnetic coupling inembodiments disclosed herein when using the pie-shaped magnets and backiron.

FIG. 6 provides a comparison of magnets as utilized in embodiments ofthe invention.

FIG. 7 depicts a comparison of maximum torque for cylindrical magnetsusing different materials in one embodiment.

FIG. 8 depicts a comparison of maximum torque for cylindrical magnetswith back iron.

FIG. 9 depicts a comparison of maximum torque for pie-shaped magnets andHalbach array

FIG. 10 depicts a graphic illustration of the relationship of torqueversus current density for the axial flux stator in one embodiment.

FIG. 11 illustrates an embodiment of the invention from a perspectiveside view.

FIG. 12 illustrates an embodiment of the invention from a perspectiveside view.

FIG. 13 (a), (b), (c) shows analyses of varying the stator length.

FIG. 14 (a), (b), (c) shows an analysis of varying the current density.

FIG. 15 (a), (b), (c) demonstrates analyses of varying the slot pitch,and resulting torque.

FIG. 16A illustrates a perspective view of an embodiment of a toothwound axial flux stator.

FIG. 16B depicts a perspective top view of the axial flux stator of FIG.16A.

FIG. 16C depicts a perspective side view of the axial flux stator ofFIG. 16A.

FIG. 16D depicts a perspective side view of the tooth height of theaxial flux stator of FIG. 16A.

FIG. 16 E depicts an embodiment of a stator core described herein.

FIG. 17 is an illustration that demonstrates as the Reynolds Numberdecreases, a point is reached where the power number begins to increasesharply, as dependent on the type of impeller utilized.

FIG. 18 charts power number, N_(p), versus Reynolds Number, N_(re).

FIG. 19 depicts the variation of impeller torque as a function ofrotating speed for Fluids 1, 2, 3, and water.

FIG. 20 illustrates the variation in torque-speed slope (dT/dn) fordifferent viscosities, as shown by Fluids 1, 2, 3, and water.

FIG. 21A shows the variation of impeller torque as a function ofrotating speed for Fluids 4, 5, 6, and water, whereby the viscosity iskept constant and density is varied to 1.1×, 1.3×, and 1.5×,respectively.

FIG. 21B shows the variation in torque-speed slope for different fluiddensities in one embodiment.

FIG. 22A is a perspective view in one embodiment of a printed circuitboard (PCB) winding incorporated between an arrangement of magnets topick up the back electro-motive force (EMF).

FIG. 22B is a graphical depiction of the torque versus load angle in oneembodiment.

FIG. 22C is an embodiment of a flux sensor, here a printed circuit board(PCB) winding, that is utilized to acquire flux information and estimatetorque.

FIG. 23 is a perspective view of an embodiment of an axial flux statorwith the magnetic arrangement, and assembled with an impeller portion.

FIG. 24 is an embodiment of bioreactor drive and impeller comprising 12magnets on each, between which the magnetic flux or the magnetic fielddensity sensor(s) are placed.

FIG. 25A shows the variation in the axial and the transverse magneticfield densities when measured on the top of the drive magnet, using amagnetic sensor, at different impeller positions.

FIG. 25B shows the variation in the axial and the transverse magneticfield densities when measured 0.125″ (3.2 mm) from the top of the drivemagnet, using a magnetic sensor, at different impeller positions.

FIG. 25C shows the variation in the magnetic flux when measured by aloop placed on the top circumference of the magnet, using PCB winding orpick-up coil, at different impeller positions.

FIG. 26 illustrates an embodiment of the mixing process in a schematicdefining the implementation of one or more sensor(s) with the mixingsystem.

FIG. 27 illustrates a flexible bioreactor bag with a rotating magneticimpeller, mounted in a rigid support vessel with a magnetic drive.

DETAILED DESCRIPTION

Various embodiments will be better understood when read in conjunctionwith the appended drawings. It should be understood that the variousembodiments are not limited to the arrangements and instrumentalityshown in the drawings.

The system and method of the embodiments disclosed pertain to a magneticdrive for a bioreactor mixer or pump that strengthens the magneticcoupling to provide higher torque and replace the drive-end magnetsand/or drive motor, as desired. Embodiments include magnetic shapes andarrangements as well, including pie-shaped magnets (“pie” shaped in thesense of a wedge shape and wedged format (i.e., triangular/trapezoidalhave a wider outer edge and smaller inner dimension, or shaped as acircular or annular sector), such that the wedges fit together toincrease the volume utilization and hence provide higher torque, andfurther allow the use of less expensive material (e.g. ferrites). In oneembodiment, the rotor side is constructed with a Halbach array whichincreases the torque. Embodiments disclosed may utilize a back iron onone or both ends to strengthen the magnetic coupling. With the Halbacharray, torque is increased without a back iron piece. Another embodimentimplements an axial flux stator to replace the drive-end magnets and thedrive motor. Embodiments are disclosed as follows.

Disposable Bioreactors

All the embodiments disclosed are applicable to a disposable bioreactor1000 as illustrated in FIG. 27. The bioreactor can comprise a flexiblebag 1001 as the bioreactor vessel, with a magnetic impeller 1002 in aninner volume 1003 of the bag. The bag is suitably configured to bemounted in a rigid support vessel 1004, comprising a magnetic drive 1005for the impeller, such that the impeller is driven by the magnetic driveand rotates around a central axis of rotation 1011 with a speed adequatefor agitating the content of the bioreactor. The bag may comprise areceiver structure 1006 for receiving the impeller and aligning it withthe magnetic drive (suitably along axis 1011), where the receiverstructure may e.g. comprise a fixed shaft or a cavity capable ofreceiving an end of a rotating impeller shaft or part of a rotatingimpeller. The inner volume of the bag can e.g. be 20-5 000 liters, suchas 50-2 000 liters. The bag may have one or more ports 1007 forintroduction and removal of materials such as e.g. cell culture media,cell inoculates, cell culture samples, nutrients, gases and/or exhaustgas. Suitably, the bag containing the impeller is suppliedpresterilized, e.g. by gamma radiation sterilization. Although themagnetic drive is here shown mounted in a bottom wall 1008 of thesupport vessel, it may also be mounted in a side wall 1009 or a top wall1010 of the support vessel. The impeller and any receiver structureshould then be placed at a corresponding position of a bag wall.

Impellers

In all the mixing/mixer system, flexible bioreactor bag and methodembodiments discussed, the impeller can be a rotating magnetic impellerdriven by a magnetic drive. The impeller is suitably capable of rotatingaround a central axis of rotation, which is suitably aligned with anaxis of the drive. The impeller may rotate around a fixed shaftcomprised in the system, but it may equally well comprise a shaft fixedto the impeller (or integral with the impeller) such that the shaftco-rotates with the impeller. Such a shaft may rotate in a cavity orbearing comprised in the system, typically forming a part of an impellerreceiver structure. The impeller may comprise one or more mixing blades,e.g. as illustrated in FIG. 17.

Pie-Shaped Magnet Configuration

For comparison purposes, FIG. 2 depicts a cross-sectional view of themagnetic field coupling 201 in a prior art system between a drive endmagnet 204 and an impeller end magnet 202; The magnetic field density203 is the area represented there between. An embodiment disclosedherein is shown in FIG. 3 where pie-shaped magnets are utilized in themixer 300. A cross-sectional view shows a large increase in the magneticfield coupling 301, the increased magnetic field density 303 between thedrive end magnet 304 and impeller end magnet 302.

FIG. 4A depicts the rotor side of a mixer 400 with a Halbach array 402in one embodiment. The individual magnets 403 are adjacent one anotherwithout spacing to form a concentric magnetic arrangement of the Halbacharray 402 around a central (rotational) axis 407. The pie-shaped driveend magnets 404 are spaced apart and positioned on a magnetic plate(back plate) 405. The magnetic plate may be a back iron, any magneticmaterial, including but not limited to any material of magneticpermeability greater than air. In one aspect, the magnetic plate may bea high magnetic permeability alloy such as an alloy comprising cobalt,iron, or other magnetic material. A magnetic field density 401 iscreated by the space remaining where the individual magnets 403 of theHalbach array 402 levitate above the drive end magnets 404.

Back Iron at Impeller and Drive Ends

FIG. 4B illustrates an embodiment of a magnetic drive 410 includingwedged (pie-shaped) magnets 412 at a drive end 413 and wedged(pie-shaped) magnets 414 at an impeller end 411, each magnet 412, 414individually positioned, angled, and spaced in a magnetic arrangementaround a central (rotational) axis 415. A magnetic plate 405 ispositioned at the impeller end 411 while a second magnetic plate 406 ispositioned at the drive end 413. The magnetic plates 405, 406 are a backiron, in one embodiment, and may be any magnetic material, including butnot limited to any material of magnetic permeability greater than air. Amagnetic field density 417 is created between the drive end magnets 414and impeller end magnets 412, thus increasing the magnetic coupling. Inanother aspect, the magnetic plate is a high magnetic permeabilityincluding materials including, but not limited to, cobalt, iron, orother magnetic material.

In one embodiment, as shown in FIG. 4C, a magnetic drive 420 includes animpeller end back iron 406 and drive end back iron 405. The cylindricalshaped magnets 418 are spaced around a central (rotational) axis 419,and positioned at each end such that a magnetic field density 421 iscreated therebetween. The back irons enhance the magnetic coupling ofthe magnetic drive, thereby increasing torque.

As illustrated in FIG. 4C, back irons are placed in the drive above theimpeller end magnets and below the drive end magnets. The back ironsreduce the overall magnetic path in air, the magnetic field density 421,between the drive end and the impeller end magnets. As a result, themagnetic field density that couples the two ends increases.

FIG. 5 depicts a cross-sectional view of a mixing system 500 showing themagnetic coupling 501 in embodiments disclosed herein when using thepie-shaped magnets and back irons, as described in FIG. 4B.

A comparison of magnets is shown in FIG. 6. Baseline torque is at about5.8 Nm with cylindrical shaped magnets as shown in FIG. 4C.

TABLE 1 Materials used for the magnets in the magnetic drive. Magnetprice Material Grade (USD/kg) Rare Sintered N42SH 70 earth NdFeB SmCo28/7 87 Non-rare Alnico Alnico 9 57 earth Ferrite CC8B/AC12 8.5

FIG. 6 illustrates that non-rare earth magnet materials, e.g., Alnico 9and C8B/AC12 (ceramic) are cheaper and have beneficial characteristicsthat align with the desired magnetic compositions, characteristics, andconfigurations described. Non-rare earth magnets may here and throughoutthe following be defined as magnets comprising less than 5 wt % of rareearth elements, such as less than 1 wt % of rare earth elements. Rareearth elements comprise elements of the lanthanide series (i.e. theelements with atomic numbers 57-71) as well as scandium and yttrium.

FIG. 7 is a comparison of maximum torque for cylindrical magnets(ϕ=0.75×0.75). By replacing Neodymium (Sintered NdFeB) magnets, andusing other non-rare earth magnets, while keeping the cylindrical shapesand arrangement, the torque production is greatly reduced.

In one aspect, a back iron may be added on one of the impeller end orthe drive end. The back iron added at impeller and drive ends improvestorque production, as illustrated in FIG. 8. Specifically, FIG. 8demonstrates the comparison of maximum torque for cylindrical magnetswith back iron, as represented in FIG. 4C. FIG. 8 shows that maximumtorque produced by different types of magnets (e.g., N 38/15, SmCo 28/7,etc.) as a function of magnet geometry. The ferrite magnet grade FB12Hgives twice the amount of the torque produced without the back plate,while eliminating the use of rare earth magnets. Three of the magnetgrades are not able to produce the baseline torque of the rare earthmagnets.

Embodiments of the invention modify the shape of the magnets fromcylindrical to pie-shaped configurations. As shown in FIG. 9, theimproved impeller-drive design provides 2.5 times the torque without theneed for expensive Neodymium magnets. Ferrite magnet grade FB12H gives2.5 times the amount of torque produced without the back plate and themagnet pie shape. As demonstrated in FIG. 4B, and referenced in FIG. 9,a comparison is shown of maximum torque for pie-shaped magnets.

Halbach Magnet Array

As shown in FIG. 9, an embodiment of the Halbach impeller-drive designof FIG. 4A provides the desired torque without the need for expensiveNeodymium magnets. This arrangement of Halbach array and pie shapedmagnets increases the torque produced by a factor of 3 which deliversthe baseline torque.

Axial Flux Stator

Embodiments of the invention provide an axial flux stator to reduce thedrive end size, as well as reducing the number of components, andincrease its reliability. FIG. 11 depicts an embodiment of the axialflux stator 110 without the shaft and bearing, and without the levermechanism as utilized in the prior art. The drive stator 111 ispositioned on an underside of the magnets 112 of the impeller end 114,aligned along a central axis of rotation 172, and has a control circuit113.

The electrical and mechanical components of the axial flux stator 110are adjusted to address challenges in the modified design. Inembodiments of the axial flux stator, the electrical componentscomprise: high current density (cooling), a higher number of slots toallow high count of slots per pole and hence the ability to choosevarious coil span (to suppress harmonics), longer slots resulting inhigher leakage inductance and lower power factor, and higher currentresults in higher flux thus accommodating a bigger stator tooth to avoidsaturation.

The construction of an axial flux stator 120 is depicted in FIG. 12 asan axial-type magnetic gear. A magnetic core 121 is here shownpositioned between a high-speed rotor 125 (stator with high frequency)and a low speed rotor 126. The magnetic core 121 has a number of slots122 depending on the arrangement of the impeller magnets and windings.The magnetic core may be laminated, powder type, or a taped core, asdesired. A set of windings are shown in FIG. 12 as stationary steelsegments 123, or stator teeth, with modulation slots 122. The set ofwindings may be tooth-wound, distributed, or fractional windings, aswell. Windings can also be single or multi-layer, wave or lap windings,full or short pitched windings. The stationary steel segments can haveadditional slotting to accommodate magnetic gearing (e.g., Vernier typemachine) with single or multi-stage gearing. The stator can also haveadditional magnets when using a Vernier type machine.

An analysis of the axial flux stator with distributed windings (e.g., aneighteen-slot example) demonstrates that by increasing the statorlength, a higher current path results per slot; saturation of the teethoccurs and causes increased harmonics (See FIG. 13). Increasing thestator current density results in higher torque; again, saturation ofthe teeth occurs and causes increased harmonics (See FIG. 14). And, byincreasing the stator slot pitch, higher torque results while placingmechanical constraints on the innermost tooth width (See FIG. 15).

FIG. 16A illustrates an embodiment of a tooth wound axial flux stator160 with nine (9) slots 165 (See FIG. 16C), for exemplary purposes, andnot limitation. FIGS. 16B, 16C, and 16D depict perspective views to moreclearly illustrate the details of the axial flux stator 160. The statorcore comprises pie-shaped magnetic stator teeth 163 that extendvertically from the stator back iron 162. The stator core 170 can beformed from sintered powdered iron, ferrite, or machined from a coil ofmagnetic steel. Conductive windings (current carrying elements) 164 arewound around the stator teeth 163. The conductive windings are dividedup into phases. Within each phase winding, the sense, field direction,of the individual coils alternates so that the application of phasecurrent to the phase winding creates a magnetic field that is directedvertically upward in one tooth and vertically downward in another tooth.The flow of current through the conductive windings forms a magneticfield that flows through the stator teeth, across the air gap betweenthe stator 160 and a rotor 161 capable of rotating around central axis172, interacts with the magnets 166 on the rotor, travels through therotor 161, and returns through a rotor magnet of opposite magneticpolarity, across the air gap between the stator and rotor, through anoppositely-excited stator tooth, closing through the stator back iron162.

As shown in FIG. 16B, the exemplary stator has nine slots 165 of widthof about 0.470 in (1.2 cm); the inside diameter (a hollow core 171 withcentral axis 172) of the stator core 170 is about 1.575 in (4.0 cm), andthe outside diameter of the stator core is about 3.250 in (8.25 cm). Thewidth of the slots, the core inside diameter, and core outside diameterare parameters that determine the performance of the motor. FIG. 16Cdepicts the magnetic stator core 170 including stator teeth 163 incombination with the base back iron 162 and shows that the stator coreis about 2.750 in (7.0 cm) height, but can vary in size, shape anddimension, as desired for a particular mixer. FIG. 16D depicts theheight of the magnetic pie-shaped stator teeth 163, the height of whichis shown here as about 2.500 in (6.35 cm). The height of the statorteeth and the thickness of the stator back iron are additionalparameters determined during the design of the stator, and so may bevaried in shape and dimension.

In one embodiment, as shown in FIG. 16E, the stator core 175 is definedwith conic teeth 176 and including a back iron 177. As such, the statorcore may be modified and designed to provide operational efficiency of amixer.

FIG. 10 compares torque versus current density of the axial flux stator160 for gaps of about 0.32 inches (0.81 cm) and about 0.265 inches (0.67cm) between the stator and rotor. More torque is produced for a givencurrent density with the smaller gap. The efficiency is slightly greaterfor the smaller gap since the current is smaller.

As demonstrated, the embodiments thus described address the problemspresented in the art. The cheaper impeller as described comprises amagnetic coupling improved by increasing the magnetic field density.Higher torque density is produced by optimizing the impeller magnet byway of material, shape, and back iron, individually or in combination.The rare earth magnets can be replaced by less expensive andenvironmentally friendly non-rare earth materials, such as Alnico andFerrite, for example. In addition, the large and oversized driveassembly used prior now can run a much smaller impeller. Further, themoving parts on the drive side, near the user have been repositioned toprovide a safer device overall.

Additional technical and commercial advantages are provided with themore reliable system that includes the axial flux stator; the axial fluxstator has a smaller drive, no moving parts, and reduced magnetic forceduring bag installation. While cost and availability of the magnets isan advantage with improving magnet shape and material, the efficiency ofthe magnetic coupling that increase torque is very useful for furtherintensification of the bioreactor, various mixing systems, and overallefficiency.

In use, for example, microbial fermentations utilize more agitation forsufficient mixing, gas mass transfer and heat transfer at the reactorwall. An improved device of the invention including the axial fluxstator improves user experience due to a less complex design. Not onlyis the design more compact than a drive with permanent magnets, but theinstallation and removal of the bag is improved as there are nopermanent magnetic forces that have to be overcome. Moving parts areavoided with consequences on machinery directive requirements, sealingand ingress protection to avoid prior standard design that utilized alever mechanism to separate the drive from the impeller such that thebag can be pulled out of the reactor bottom end piece.

Various embodiments will be better understood when read in conjunctionwith the appended drawings. It should be understood that the variousembodiments are not limited to the arrangements and instrumentalityshown in the drawings.

Torque produced in the mixing process relates to different fluidproperties such as viscosity and density. Torque also relates todifferent mixing conditions such as presence of obstacles and changes orissue with gas sparging. For example, disruption of the continuousliquid or sparger liquid by zones of air presents large bubbles orchannels, a behavior typically called [gas] flooding of the mixer; thisleads to a drastic reduction of power input. A torque measurement (i.e.a continuous measurement in real time) under conditions close to or atthe point of flooding of the mixer allows for better process control andhigher utilization of mixing power, including improved capacity andcapability in the process step. For example, a bioreactor could operateat higher mass transfer and thus higher productivity. Moreover, torquemeasurements, along with speed, enable determination of powertransmitted to fluid by actual measurement, in contrast to using solelyempirical impeller power number and speed, and thus allow actual masstransfer determination (i.e., gas transfer calculations). As describedherein, embodiments refer to a torque and speed sensor, such as atransducer, and a method of using the measured torque and speed todetect the different fluid and mixing properties, conditions, andabnormalities.

Mixing Power

Embodiments of the invention disclosed allow the power consumed by arotating impeller to be easily measured in a process fluid. The unitsexpress this power as ‘horsepower’ (HP). Mixer performance relates tohorsepower; problems, however are associated with this tendency. Ingeneral, Power (P) input to the fluid can be calculated for typicalmixers (turbulent flow) applications as follows:

$\begin{matrix}{P = \frac{\rho \; N_{p}N^{3}D^{5}}{g_{c}}} & \left( {{Eq}\mspace{14mu} 1} \right)\end{matrix}$

-   -   =Specific Gravity    -   N_(p)=Power Number of Impeller    -   N=Impeller Speed    -   D=Impeller Diameter    -   g_(c)=dimensional constant

Viscosity Effect

As viscosity increases, the impeller power number may begin to increase.This becomes important in the HP calculations because as power numberbegins to go up so does the horsepower utilized to drive the mixer.Simply increasing the input [horse-] power may be the answer, but thischange reduces the service factor of the mixer drive, hence a ‘bigger’mixer may be required. Viscosity increase also affects the flowcharacteristics of fluid as compared to water.

Reynold's Number

Reynolds Number is a dimensionless number that can be derived asfollows:

$\begin{matrix}{N_{re} = \frac{D^{2}N\; \rho}{\mu}} & {{Eq}\mspace{14mu} (2)}\end{matrix}$

-   -   ρ=Fluid Density    -   μ=Viscosity

The power number (N_(p)) is constant for each impeller type, as long asthe Reynolds number is sufficiently high. The power number is a functionof Reynolds Number (N_(re)).

The illustration of FIG. 17 shows how the power number for each impellervaries with changes in Reynolds Number. As the Reynolds Number drops, apoint is reached where the power number begins to increase sharply. Thispoint depends on the type of impeller in use. Reynolds Numbers or N_(re)between 1000 and 2000 are generally considered “in transition”.

The Reynolds number is the indicator of the type of mixing fluid inwhich the mixer will operate. If the Reynolds Number is above 2,000, thepower number is constant, When the Reynolds Number calculated is lessthan 1,000 (i.e., laminar flow), then the power number increases as theReynolds Number decreases. Consequently, the shaft horsepower calculatedis based on the corrected power number. In this case, as shown in FIG.18, a power number (N_(p)) vs Reynolds Number (N_(re)) curve is obtainedfrom the impeller manufacturer or by experimentation.

In embodiments of the invention, the power utilized to mix a fluid at agiven speed can vary based on multiple parameters, including but notlimited to: (i) the impeller diameter, (ii) the impeller blade design,(iii) the fluid properties (i.e. viscosity and density). In someapplications, such as mammalian cells mixers, controlling the powerdelivered to the fluid is an element of the mixing process. Since themixing power is driven by the drive system, it can be measured andcontrolled from that side. The drive system can be in the form of astator that rotates the impeller, or a set of magnets coupled to theimpeller magnets and driven by a separate motor. In these embodiments,the magnetic field that couples the drive to the impeller depends on thepower (and also torque) delivered to the impeller. By measuring themagnetic field or flux, the torque, speed, and power delivered to theimpeller can be calculated and hence controlled. Further, the currentand voltage inputs to the drive system are related to the powerdelivered to the system. These values can also be used to calculate thepower delivered to the impeller.

Characterizing a Fluid

Fluid properties of density p and viscosity μ play a role in specifyingthe desired mixing power and torque, as these properties are representedin the Reynolds number calculation as well as in the specific powerequation. In estimating such parameters, for exemplary purposes, and notlimitation, curve #4 from the FIG. 17 is shown in FIG. 18.

Next, the torque-speed curves are plotted for seven different fluids:water, and six other fluids with different density, dynamic viscosity,or combination of both, than water. Table 1 shows the general propertiesof each fluid (at 25° C.) while Table 2 shows the impeller and tankproperties.

TABLE 1 Fluid Fluid Fluid Fluid Fluid Fluid Property Water #1 #2 #3 #4#5 #6 Fluid Density, ρ 1000 1000 1000 1000 1100 1300 1500 [kg/m³]Dynamic 0.00089 0.0089 0.089 0.89 0.00089 0.00089 0.00089 Viscosity, μ[Pa · s]

TABLE 2 Property Value Impeller Diameter [in] 3.5 Tank Volume [Lit] 200

The calculation for the torque-speed characteristics are done usingequation 1 (Eq. 1) and equation 2 (Eq. 2). FIG. 19 shows the variationof impeller torque as a function of rotating speed for Fluids 1, 2, 3,and water. The viscosity is the variable parameter in this calculation.Fluid 1 does not show detectable variation from water, while Fluid 2 andFluid 3 show differences due to the increase in viscosity (100 times forFluid 2 and 1000 times for Fluid 3).

FIG. 20 shows the variation in torque-speed slope for differentviscosities. The variation in slope is minimal when varying theviscosity, while the variation in y-axis crossing point isdifferentiated. Again, Fluids 1, 2, 3, and water are plotted; Fluid 1does not show detectable variation from water.

FIG. 21A shows the variation of impeller torque as a function ofrotating speed for Fluids 4, 5, and 6 as compared to water. Theviscosity is kept constant and density is varied (relative to thedensity of water) to 1.1×, 1.3×, and 1.5×, respectively. The variationof density is detectable for the fluids.

FIG. 21B shows the variation in torque-speed slope for different fluiddensities of Fluids 4, 5, and 6 as compared to water. While thevariation in slope due to viscosity is minimal, the density effects theslope, and minimally, the y-axis intercept.

Hence, following the relationships outlined above, the change ofviscosity in a fluid may be detected by measuring the impeller torque atdifferent speeds. In addition, changes in density are detectable atvarious levels. By studying the torque-speed slope, the variation influid properties can be distinguished between variations in viscosity ordensity.

Embodiments below describe the method of measuring the torque forbioreactors and various types of mixers.

To measure the torque and speed of an impeller, transducers can beinstalled on the shaft, in the space between the impeller and drive, onthe impeller magnets, or on the drive magnet or core as additionalcomponents.

Method 1: Measuring Torque and Speed as Related to Magnet-MagnetCoupling

Embodiments of the invention include a sensor positioned outside a bagor vessel, outside the closed system, that does not allow for electricalwiring inside the bag. In one aspect, the sensor is integrated with thedrive head. FIG. 22A depicts a system 600 with a printed circuit board(PCB) winding 602 incorporated with an arrangement of magnets 603, 604of an axial flux stator 605. The system 600 includes a first set ofmagnets 603 at the impeller end 607 (rotatable around central axis 608),the impeller end positioned within a vessel 601, and a second set ofmagnets 604 positioned at the drive end 605. The PCB winding 602 is asingle coil, or set of coils as shown in greater detail of FIG. 22C, andplaced between the sets of magnets 603, 604 in the area 606 where themagnetic gradient is arranged. FIG. 22B demonstrates that synchronoustorque depends on load angle, such that the angle between the rotor andthe stator fluxes (i.e., the angle between the rotor pole (or magnet)and the stator pole (or magnet)). By placing a single coil or a set ofcoils, such as the printed circuit board (PCB) winding 602, between thestator 605 and the rotor 607, the magnetic flux in the space or area 606between the drive and the impeller (partially or fully filled with air)can be detected and related to the produced torque. In one aspect, asingle coil or the set of coils are printed on a circuit board, and canbe arranged and placed in a single layer or multi-layers.

In one embodiment, a flux sensor, such as the PCB winding 602 (shown inFIG. 22C) is installed on an existing magnet-magnet coupling of abioreactor, or mixer system, to acquire flux information and estimatetorque. The flux sensor functions to acquire the speed by relating themeasured voltage to the speed of rotation. The voltage, as it changeswith time, is measured at various instances. In FIG. 22C, theillustration depicts a PCB winding 602 that picks up the backelectro-motive force (EMF).

In one embodiment, a magnetic field density sensor 808 (e.g., one ormore 3D hall-effect based sensors, anisotropic magnetoresistance (AMR),shingled magnetic recording (SMR), giant magnetoresistance (GMR)sensors), and shown in FIG. 24, is installed in the space between thedrive and the impeller. The magnetic field density in this space changesas the torque produced by the impeller changes. FIG. 24 depicts amagnet-magnet coupling bioreactor system 800, using integrated sensors808 to measure the varying viscosity and varying density when the systemis in use. Impeller magnets 810 at the impeller end 802 form a firstportion and the drive-end magnets 806 incorporate with a base steelplate 804 form a second portion. As depicted, sensors 808, includingmagnetic field density sensors, are integrated with a drive magnet 806.The sensors, however, may be incorporated, integrated, and/or placedwithin any region of the system 800. Specifically, the sensors shown areintegrated within the region 811 between the impeller-end magnets andthe drive-end magnets. The produced torque relates to the fluidproperties (e.g., weight, volume, viscosity, density). At speed n dT/dn,T is used to identify fluid viscosity, density, and different operatingconditions.

Method 2: Measuring Torque and Speed as Related to Axial Flux (AF)Stator

With the axial flux stator, as shown in FIG. 23, the stator voltages andcurrents are acquired and decomposed to direct and quadrature axiscomponents, and back EMF and torque are calculated without the need forsensors. FIG. 23 illustrates an embodiment of a device 700 having afirst rotor portion 707 positioned within a vessel 701, and a secondstator portion 705; the second stator portion is a tooth wound axialflux stator 705 that comprises pie-shaped magnetic stator teeth 763 thatextend vertically from the stator back iron 762. The stator core can beformed from sintered powdered iron, ferrite, or machined from a coil ofmagnetic steel. Conductive windings (current carrying elements) 764 arewound around the stator teeth 763. The conductive windings are dividedinto phases. Within each phase winding, the field direction of theindividual coils alternates so that the application of phase current tothe phase winding creates a magnetic field (B) that is directedvertically upward in one tooth and vertically downward in another tooth.The flow of current through the conductive windings forms a magneticfield that flows through the stator teeth, across the air gap, or region706 between the stator 705 and a rotor 761, interacts with the magnets703 on the rotor, travels through the rotor 761, and returns through arotor magnet 703 of opposite magnetic polarity, across the air gapbetween the stator and rotor, through an oppositely-excited statortooth, closing through the stator back iron 762.

While Method 1 is described in terms of the magnet-magnet couplingsystem 800 and can be applied to several different arrangements of driveand impeller, Method 2 is specific for wound stator drive system 700 asshown in FIG. 23. The magnet-magnet coupling system leverages the changein magnetic field density and/or magnetic flux to produce information onthe position of the impeller and hence, the produced torque and/orspeed. The stator drive system acquires the input current and voltage tothe wound stator and relates such information to the produced torqueand/or speed.

FIG. 25A shows a comparison of the magnetic field density acquired onthe center point 899 of a top surface 898 of one drive magnet 806 (seeFIG. 24) for different impeller positions. Impeller positions arerecorded as the angle difference between the center line of the impellermagnets 810 and the corresponding center line of the drive magnet 806.The density of the magnetic field is recorded in both axial andtransverse directions and it shows significant differences as theimpeller-drive angle changes. These values are directly related to theproduced torque and are used to deduce the produced torque.

FIG. 25B is similar to figure FIG. 25A with the difference of the pointof measurement. Here, the point of measurement 897 is shifted ⅛^(th) ofan inch (3.2 mm) in the axial direction towards the impeller, the pointof calculation is 0.125″ (3.2 mm) above the center 899 of the drivemagnet 806. Again, the changes in magnetic field density is relative tochanges in the impeller magnet 810 position. The sensor position can beanywhere between the drive and the impeller, or even on the bottomsurface of the drive or the top surface of the impeller.

FIG. 25C shows the change in magnetic flux for different impellerpositions. It is clear that the magnetic flux can also be used to detectthe impeller position and hence the produced torque. Since the fluxchanges with impeller relative position, it can be used also to detectsudden impeller position, relative to drive, changes. This can beexplained using Faraday's law:

$e = {{- N}\frac{d\; \varphi}{dt}}$

Here, e is the produced voltage in the loop, used to pick-up themagnetic flux, N is the number of turns of the loop, and ϕ is themagnetic flux through the loop 896. A change in the impeller relativeposition causes a sudden change in the loop voltage (since the voltageis related to the time-change on the magnetic flux) and hence, thischange in voltage can be related to the change in the impeller relativeposition. If the impeller speed increases over a certain time (t), thenthe voltage during this period can be used to calculate the new impellerrelative position and speed. If the impeller changes relative positionsuddenly, due to an abnormal condition, then the voltage waveform isvery short in time (more like a pulse) and hence an abnormality behaviorcan be detected and a subsequent action triggered.

FIG. 26 is a schematic of a mixer system 900. In one aspect, the mixersystem is a pump. In another aspect, the mixer system is a bioreactorsystem. The mixer 900 includes a controller 902; a drive 904 includes astator, a motor, magnetic coupling, among other components; and animpeller 906 includes one or more blades, among other components. Thecontroller 902 controls the mixer and/or pump drive 904. The drive mayinclude any one of a stator, motor, magnetic coupling, alone or incombination. The sensor arrangement 907 includes a torque-speed sensor908, a current/voltage/flux sensor 910, alone or in combination. Thesensors 907 relay information to a processor 912 which analyzes thetorque and speed calculation, analyzes power provided to the fluid,fluid properties (e.g., density, viscosity, etc.), mixing properties(e.g., change in fluid properties, abnormalities in mixing, blockage,gas dispersion, etc.), and other analyses as selected. The processorthen provides direction to the controller 902 in a feedback loop. Inthis manner, the processor is an analyzer that provides precise controlof the mixer to increase or decrease agitation, direct power into thesystem, adjust fluid properties, and correct any deficiencies,abnormalities, or otherwise.

Aspects herein include the assessment of the angle in between the driveand the impeller during mixing operations. This allows for determinationof torque, viscosity, and other fluidic properties. This provides acommon feature between the dedicated sensor (See FIG. 22C, sensor 602)and the indirect measurement with the axial flux stator.

In one embodiment, the angle in between the drive and the impeller isdetermined by optical methods such that a marker on the impeller is readby an optical detection system. In such an embodiment, reflecting lightfrom a fiber would allow ease of detection as the impeller is close tothe bag bottom and a transparent window can fit with the bag. Otherposition indicators are possible as well.

In one embodiment, a discrete Hall sensor is utilized. The signal can beprocessed and compared against the position of the drive, in either arotating drive or a flux stator. Calibration for a zero torque (offset)case without liquid or other conditions can also be configured. The useof a magnetic field sensor, direct or indirect, can thus be modified andaltered in size, shape, and dimension as desired by a user.

Embodiments disclosed herein have several advantages to supersedesystems in the field today. Such benefits include detection of fluidviscosity and density, as well as power and torque, delivered to thefluid inside the mixer. Obstructions are detected during start-up,including for example, sediment of micro-carriers, cells or undissolvedpowder in the bottom of the mixer. Torque measurements enabledetermination of power transmitted to fluid by actual measurement, incontrast to using solely empirical impeller power number and speedaccording to Eq. 1), hereby allowing for actual mass transferdetermination (e.g., gas transfer calculations). In addition, floodingof the impeller in multiphase systems (e.g., gas sparged bioreactor) canbe detected. Changes and any issues in gas sparging can be detected.Correct positioning of the disposable unit, and its impeller, can beverified. Measurement and monitoring of the different properties canalso be used for the process analytical tool (PAT).

Embodiments further address the challenges and issues that arise in thefield. Determination of power delivered to the fluid is currentlyperformed with formulas or look-up tables and not directly measured.Fluid density and/or viscosity changes as the mixing process takesplace, thus, updated values provide accurate control of the mixingprocess. Abnormalities in mixing process, such as blockage, obstacles,or issues with gas sparging, may also be determined to ensure quality ofthe mixing process. These features detect and flag such issues, possiblyeven providing an alarm, so that the mixing process can be corrected.

Embodiments disclosed herein provide additional functionalities to theuser of the bioreactor or mixer, as desired. Various embodiments allowaccurate monitoring of the power delivered to the fluid while mixing,and allow continuous updates on the fluid properties, including alarmsin cases of abnormalities in mixing. Such embodiments may be modified soas to encompass features and components such as temperature, pressure,and other measurable conditions. The embodiments and aspects disclosedherein may be incorporated with any size, shape, and dimension ofvessel, bag, mixing container or otherwise.

It is to be understood that the above description is intended to beillustrative, and not restrictive. For example, the above-describedembodiments (and/or aspects thereof) may be used in combination witheach other. In addition, many modifications may be made to adapt aparticular situation or material to the teachings of the inventionwithout departing from its scope. Dimensions, types of materials,orientations of the various components, and the number and positions ofthe various components described herein are intended to defineparameters of certain embodiments, and are by no means limiting and aremerely exemplary embodiments. Many other embodiments and modificationswithin the spirit and scope of the claims will be apparent to those ofskill in the art upon reviewing the above description. The scope of theinvention should, therefore, be determined with reference to theappended claims, along with the full scope of equivalents to which suchclaims are entitled. In the appended claims, the terms “including” and“in which” are used as the plain-English equivalents of the respectiveterms “comprising” and “wherein.” Moreover, in the following claims, theterms “first,” “second,” and “third,” etc. are used merely as labels,and are not intended to impose numerical requirements on their objects.

This written description uses examples to disclose the variousembodiments, and also to enable a person having ordinary skill in theart to practice the various embodiments, including making and using anydevices or systems and performing any incorporated methods. Thepatentable scope of the various embodiments is defined by the claims,and may include other examples that occur to those skilled in the art.Such other examples are intended to be within the scope of the claims ifthe examples have structural elements that do not differ from theliteral language of the claims, or the examples include equivalentstructural elements with insubstantial differences from the literallanguages of the claims.

1-135. (canceled)
 136. A magnetic mixing system to characterizeconditions in a fluid mixing device, the system comprising: a mixervessel comprising a fluid; a drive that creates a magnetic field; acontroller that operates the drive; one or more magnet sensorsconfigured to detect the magnetic field or a magnetic flux, andpositioned with the system to detect the magnetic field or the magneticflux; and a processor receiving information from the one or moremagnetic sensors, the processor configured to provide direction to thecontroller based on at least one of: the continuous calculation of atleast the torque and speed delivered in mixing the fluid, or thecontinuous characterization of at least one of: a plurality of fluid andmixing properties, a plurality of mixing conditions, and a plurality ofabnormalities while mixing the fluid.
 137. The magnetic mixing system ofclaim 136, further comprising an impeller inside the vessel, wherein thedrive creates the magnetic field to rotate the impeller and the one ormore magnet sensors measure the magnetic field or the magnetic fluxprovided to the impeller.
 138. The magnetic mixing system of claim 137,wherein the one or more magnet sensors are positioned with the drive,the impeller, or between the impeller and the drive.
 139. The magneticmixing system of claim 136, wherein the one or more magnet sensorsfurther detect current and voltage provided to the drive.
 140. Themagnetic mixing system of claim 136, wherein the drive is a stator, orthe drive includes a set of permanent magnets in combination with amotor.
 141. The magnetic mixing system of claim 136, wherein the driveis a stator, motor, or magnetic coupling, and the one or more magnetsensors are transducers positioned therewith, respectively, alone or incombination.
 142. The magnetic mixing system of claim 136, wherein thetorque and speed of the impeller corresponds to the torque and speeddelivered in mixing the fluid.
 143. The magnetic mixing system of claim136, wherein the processor uses the power, torque or speed, alone or incombination, with one or more fluidic properties to assess real-timemixing conditions and mixing properties.
 144. The magnetic mixing systemof claim 143, wherein the processor detects a change in the fluidicproperties, mixing conditions, or mixing properties, individually or incombination.
 145. The magnetic mixing system of claim 136, wherein theplurality of abnormalities comprises abnormalities in the fluidproperties, mixing conditions, or mixing properties and the processordetects the plurality of abnormalities as determined by learned patternsor predetermined threshold values.
 146. The magnetic mixing system ofclaim 136, wherein the plurality of fluid and mixing properties includedensity and viscosity of the fluid.
 147. The magnetic mixing system ofclaim 146, wherein the processor is configured to detect abnormalitiesin the density or viscosity of the fluid, in the power, torque, orspeed, alone or in combination.
 148. The magnetic mixing system of claim136, wherein the processor is configured to detect blockage, gasdispersion, or one or more contaminants in the fluid, alone or incombination.
 149. The magnetic mixing system of claim 136, wherein theprocessor comprises an analyzer that provides the direction to thecontroller in a feedback loop.
 150. The magnetic mixing system of claim149, wherein the analyzer directs power to the drive to increase ordecrease agitation, to adjust fluidic properties, and correct anydeficiencies or abnormalities, individually or in combination.